Apparatus for the liquefaction and rectification of air.



H. FILIPPO & P. SCHOONENB ERG. APPARATUS FOR THE LIOL JEFAC TION AND RECTIFICATION OF AIR.

APPLICATION FILED JUNE 3- I916.

m @M 0 0 J 5. d Z1 m U l] m 4 ,w 1 m 2 4 4 ,1, 9. x /z% UNITED STATES PATENT OFFICE.

HENDBIK FILIPPO AND PANCRAS SCHOONENIBEBG, OF EINDHOVEN, NETHERLANDS,

ASSIGNORS OF ONE-THIRD TO NAAMLOOZE VENNOOTSCHAP PHILIPS METAAL-GLOEI- LAMPENFABRIEK, OF EINDHOVEN, EMMASINGEL, NETHERLANDS, A LIMITED LIA- BILITY COMPANY OF THE KINGDOM OF THE NETHERLANDS.

APPARATUS FOR THE LIQUEFACTION AND RECTIFICATION OF AIR.

Specification of Letters Patent.

Patented Feb. 26, 1918.

Application filed June 3, 1916. Serial No. 101,442.

To all 'whom it ma concern:

Be it known t at we, HENDRIX Frmrro and PANCRAS SCHOONENBERG, subjects of the Queen of the Netherlands, residing at Eindhoven, Netherlands, have invented certain new and useful Improvements in or Relating to Apparatus for the Liquefaction and Rectificatlon of Air, of which the following is a specification.

In the known apparatus for the production of oxygen from atmospheric air by li uefaction and rectification in a single co umn the drawback is met with that the oxygen cannot be made with a higher percentage than 95-97% without'substantially diminishing the yield.

This drawback is due to the nature of the gases which contaminate the oxygen in the lower part of the column. By several experiments we have found that these impurities, besides containing small quantities of nitrogen, are composed chiefly of argon. As argon has a boiling point betweenthe boiling-points of oxygen and nitrogen and very near to that of oxygen, it is impossible to remove this argon together with the nitrogen out of the upper end of the rectification column without losing at the same time a lar e part of the oxygen with this nitrogen, an thus diminishing substantially the yield of the apparatus.

On the other hand, if the yield of the apparatus is maintained as high as possible, by allowing the nitrogen to escape from the upper part of the apparatus with as little.

as possible of oxygen, nearly all the argon of the air is kept back in the oxygen. As atmospheric air contains nearly 1% of argon, this percentage might rise to about 4% in the oxygen.

According to the invention however the technical requirements of the production of oxygen as pure as possible and a large yield of the apparatus are united.

A hitherto unknown important improvement is applied to the rectification column, by which it is possible to remove argon from the oxygen without losing large quantities of oxygen. This improvement consists 1 n bullding in the inner part of the rectification column, in which the rectification of the air is carried out, a second rectification column, be inning where the impurity of the oxygen chlefly copsists of argon, and being closed at its upper end. In this column the argon containing gas mixtures may rise upward and as this column is surrounded by layers of gas and liquid, becoming gradually colder in the upward direction, a second rectificatipn of this gas mixture automatically takes p ace.

If now from this second inner column the noncondensed gases are allowed to escape, it is possible in this way, without a considerable loss of oxygen, to remove argon out of the apparatus and thereby to improve considerably the percentage of the oxygen. Besides the considerable. improvement of the purity of the oxygen, by which it becomes more fit for the cutting of metals such as iron, a considerable quantity of a gas rich in ar on is obtained which is commercially usegul, e. g. in the manufacture of incandescent lamps.

The accompanying drawings explain more or less diagrammatically the manner in which thedescribed improvement is applied to a rectification apparatus.

1 is an air rectification column, communicating at it upper end by a perforated plate 21 with a heat exchanger 2, and at its lower end with a bath containing liquid oxygen 3. \Vhen the apparatus is working, compressed air (for instance of 80 atm. pressure) is admitted at 6, and flows through the heat-exchanger consisting of a large number of coils 61 which are cooled by the cold nitrogen escaping from the main column through the plate 21 into the space sur rounding the coils 61 and from there through holes in the top plate 22 into the chamber 23 and leaving the apparatus at N The cylindrical space 10 in the center of the heatexchanger is filled up with isolating material and may contain a pipe 11 extending into the top of the main column through' which liquid air may be passed to start the apparatus or by which the pressure may be measured.

After leaving the heat-exchanger the compressed air passes through a tube 62 to the oxygen bath 3 in which it is wholly or partly liquefied in coils 63, from which it passes through cook 64 and tube 65 somewhere into the upper part of the main column (for instance, at 66).

In this column it is separated by rectification into vapors which are richer in nitrogen and liquids which are richer in oxygen. The liquid flows downward, becoming more and more rich in oxygen and collects in 3. In 3 the liquid is boiled by the compressed air in coil 63. Part of the vapors produced by this boiling rises again into the column, another part escapes through tube 7 and coils 71 and is recovered at 0 Between the coils 71 are coils 81; together these coils surround the coils 61 and may be separated from them by a cylindrical plate 72 which may form or not a hermetical separation.

Into the coils 81 nitrogen of about 5 atm. pressure is fed through 8. The coils 71 and 81 interchange heat and the cooled nitrogen leaves the heat-exchanger through tube 82 which leads to coils 83 in the oxygen bath 3 where the nitrogen is liquefied and from there through cook 84 into the top of the main column at 86.

The temperature in the top of the column 1 may be measured by a thermometer extending through tube 12. The part 8-86 is not necessary, if only oxygen and argon are to be produced but is required, if pure nitrogen is desired.

'The pure liquid nitrogen, entering the column at 86 helps verymuch the rectification of the vapors between outlets 66 and 86. The coils 83 assist in boiling the oxygen. The bath 3 is connected at its lower and upper ends with tubes 9 and 91 which are connected to a water manometer showing the level of the liquid in the oxygen bath3.

As far as described the column has .nothing particular and may be worked as an ordlnary air-rectlficatlon column glvlng substanti ally pure nitrogen and about 95% oxy-.

.4 is constructed, which is wholly surrounded by the main column and communlcates with it only at the bottom at 41. The inner-column 4 is closed at the top, but has one or more gas outlets 13 (131, 132, 133, 134) the highest being preferably placed at or near the to These gas outlets lead from different heights of the inner column and are controlled by cocks K K outside the apparatus.

When the cocks K K are closed, the column 4 does not work and the main column will work as an ordinary air-rectification column, but when one of the cooks K K is opened, the column 4 begins to work. The vapors at 41 in the main col-- temperatures of which decrease with the height, the rising gaseous mixture is cooled and partly liquefied. The liquid contains chiefly oxygen, the argon accumulates in the gaseous parts. The construction of the inner column and the gradually decreasing temperature in the outer column assure an excellent rectification in the inner-column.

The "vapors containing chiefly argon, are withdrawn by one of the cooks K -K the liquefied parts return into the main column.

In the lower part of the main column, below the inner-column, this liquid together with the condensate of the main column is rectified into pure oxygen, which accumulates in 3 and a gaseous mixture of oxygen and argon, which rises partly into the main column, and artly into the inner-column. The part rising into the main column is continually liquefied and returned, together with the oxygen and argon of the fresh air, so that argon would accumulate unduly, but this is prevented by the inner-column, by which, in state of equilibrium, as much argon is drawn oil as is liquefied out of the fresh air by the main column.

In the industry many examples are found I of a process for the separation of several in which at'first a partial separation of the constituents is obtained and afterward the productsare separated further in a second apparatus. -This same process might be applied in the separation of atmospheric air (by means of liquefaction, followed by rectification) into itschief constituents, nitrogen, oxygen and argon. In this case one removes nearly all the nitrogen from the air as the first step, While the residual mixture of oxygen and argon in which still some ni-' trogen is present, may be separated in a second apparatus.

In general this process has no particular difliculties for ordinary'distillation processes.

This is not so, however in the rectification of air.

In the separation of gases by means of liquefaction and rectification the apparatus are always working more economically. the more the heat-exchanging with the surroundings is restricted, or the more perfect the regeneration of the cold of the gases coming into or out of the apparatus. In this respect the construction according to this invention has particular advantages. The loss of cold by.

the dimensions of the rectification column increase only slightly by building the much therefore the loss of cold from the outer column increases only slightly while the loss of cold of the inner column, being built wholly within the first column, is reduced to zero. A separately'mounted column on the contrary would present a considerable extended surface, accompanied by an increase of loss of cold.

A further advantage of this construction is that in the second or inner column, which is Wholly'surrounded by the layers of gas and liquid in the outer column which gradually become colder in the upward direction, a distribution of temperature is obtained which furthers a good rectification and makes it possible to withdraw gas in different places and therefore at different zones of temperature of the inner column by which gas mixtures with the desired percentage of argon or nitrogen may be obtained. The providing of gas-outlets at different, heights of the inner column makes it possible in this apparatus to reduce or extend the working length of this column and therefore the temperature-drop between which the rectification takes place.

Further advantages of the built-in rectification column are that it'is always ready for rectification as soon as the outer column works, and that it begins to Work as soon as gas is allowed to escape out of the inner column, while it stops its action as soon as the gas-escape is stopped, in which case the outer column is used as a single column.

For keeping the rectification going in the inner column, no particular means are necessary. When carrying out the rectification in a separately mounted column, this column requires firstly to be made ready for use (cooled) for which, as also for keeping the rectification going, extra means are neces sary, requiring extra regulation and super- VlSlOIl.

Further advantages are the simplicity of construction of the apparatus and the small space required by the apparatus.

What we claim is:

1. An apparatus for liquefying and rectifying air, comprising a main rectification column, a second rectification column within and completely surrounded by said main column, said inner column being open at its bottom to said main column, and means for drawing gas from said second column at various heights.

2. An apparatus for liquefying and rectifying air, comprising a main rectification column, a second rectification column within and completely surrounded by said main column, said inner column being open at its bottom to said main column, a heat-exchanger at the upper end of the main column, a bath containing liquid oxygen at the lower end of said column, means for admitting air into the apparatus through the heat exchanger and the oxygen bath successively,

a closure for the top of the second rectification column, and means for drawing gas from said second column at the top and at various heights.

3. An apparatus for liquefying and rectifying air, comprising a main rectification column, a second rectification column within and completely surrounded by said main column, said inner column being open at its bottom to said main column and means for drawing gas from said second column.

In testimony whereof we have hereunto set our hands in presence of two subscribing witnesses.

HENDRIK FILIPPO. PANCRAS SCHOONENBERG.

Witnesses D. KLUJN, KURD BAAQUET. 

